Research Aims: A disparity in patient outcomes exists in the treatment of cancer in developed and developing countries. Contributing to this disparity are the relatively limited resources in developing countries, including technology, expertise, and training of clinical personnel. Our long-term research goal is to reduce the probability of late effects from cancer radiotherapy by reducing the level of disparity between children in developed and developing countries. Because proton therapy reduces exposure to normal tissues, we believe that using it rather than photon therapy for regional craniospinal irradiation of childhood cancer of the central nervous system (CNS) will significantly reduce the risk of late effects. However, we expect that proton therapy carries no advantage in conformal irradiation of localized brain cancer. Therefore, it is our hypothesis that a statistically significant disparity between developed and developing countries exists in pediatric patient outcomes following regional radiotherapy and that this disparity is not significant for localized treatment. Testing this hypothesis requires knowledge of the radiation exposures to organs at risk from the best available treatment modalities in developing and developed countries. The following specific aims will test the hypothesis: (1) In a virtual clinical trial, quantify the disparity in outcomes of children receiving regional (craniospinal) irradiation for CNS cancer according to the standard of care in a developing country versus that in a developed country. (2) In a virtual clinical trial, quantify the disparity in outcomes of children receiving three-dimensional conformal radiotherapy for a localized brain tumor according to the standard of care in a developing country versus that in a developed country. Career Development Aims: My short-term career development goal is to receive training as an international research scientist. The environments in the supporting institutions offer a unique opportunity to accomplish this. The University of Texas M. D. Anderson Cancer Center is a premier cancer center with state-of-the-art radiotherapy technologies. The American University of Beirut Medical Center is a leading specialty hospital treating cancers in a developing country in the Middle East and an internationally recognized research institution. Under the mentorship of established leaders in radiation oncology research, this work seeks to build on the partnership between the two institutions, sharpen my skills in addressing a global health problem, and prepare me to become an independent cancer researcher in an international context. I will accomplish this by enhancing my clinical research skills, improving my competitiveness for future research funding, and forging a network of collaborators in the Middle East.